1. Field of the Invention
The invention relates to a display apparatus, and more particularly, to a liquid crystal display (LCD).
2. Description of Related Art
With advantages of high definition, small volume, light weight, low driving voltage, low power consumption, and extensive range of application, liquid crystal display (LCD) has become a mainstream among various display products. The conventional LCD panel is constituted by a color filter substrate, a thin film transistor (TFT) array substrate, and a liquid crystal layer sandwiched therebetween. However, this LCD panel has low resolution and pixels thereof have low aperture ratio. Moreover, misalignment easily occurs when bonding the color filter substrate and the TFT array substrate. Recently, techniques including color filter on array (COA) and black matrix on array (BOA) have been proposed. Specifically, a COA substrate or a BOA substrate is assembled with an opposite substrate without having a color filter layer or a black matrix layer formed thereon. Liquid crystal (LC) molecules are then filled between the two substrates to form an LCD. Since the color filter layer is formed on the TFT array substrate directly, misalignment almost does not occur. Further, this LCD panel has superior resolution and the pixels thereof have high aperture ratio.
FIG. 1 shows a partial cross-sectional view of a storage capacitor of a pixel in a conventional LCD. As shown in FIG. 1, an LCD 100 includes a TFT array substrate 110, an opposite substrate 120, and an LC layer 130. Here, the TFT array substrate 110 has a color filter layer 150 disposed between a pixel electrode 140 and a substrate 112. It should be noted that in the LCD, in order to increase the capacitance of the storage capacitor of the pixel, the color filter layer 150, which is disposed above a capacitor electrode 142 of the pixel, is usually removed entirely to reduce a distance between the pixel electrode 140 and the capacitor electrode 142 for increasing the capacitance of the storage capacitor of the pixel.
Nevertheless, an excavated region of the color filter layer 150 on the TFT array substrate 110 forms into a recess region (i.e. an X part in FIG. 1). Thus, the amount of LC molecules has to be increased during the filling to fill the recess region. Also, defects such as bubbles are easily generated in the recess region during the process of filling LC molecules, and this consequently leads to mura. In addition, since orientation of the LC molecules is hard to be controlled due to the taper of the color filter layer 150, disclination phenomenon (i.e. a Y part in FIG. 1) of the LCD 100 occurs. Furthermore, the taper of the color filter layer 150 also leads to light leakage phenomenon, contrast ratio reduction, and poor display quality.